The invention relates to a heat exchanger for a motor vehicle, in particular for a motorcycle, having a first and a second collecting tank and a curved heat sink arranged between the collecting tanks, so that flow can pass through it, also having lateral connecting planes for attachment to the collecting tanks and having a longer side and a shorter side between the collecting tanks.
Cooling of efficient internal combustion engines in motor vehicles is usually accomplished by using a coolant which absorbs heat in areas of the internal combustion engine that are to be cooled and releases this heat elsewhere via a heat exchanger through which air can flow. The evolution of heat and thus the requirement for dissipation of heat via the heat exchanger depend on the power of the internal combustion engine. Very powerful internal combustion engines require especially effective heat exchangers having the largest possible surface area exposed to oncoming flow.
Especially in the motorcycle area, however, the available surface area is limited. With very powerful internal combustion engines, in particular and/or when very little space is available because of design factors, very complex measures must sometimes be taken to ensure an adequate cooling capacity.
An efficient heat exchanger for a motorcycle is known from the Honda company Fireblade brochure of Feb., 2004; in the installed position, this heat exchanger has an oncoming flow surface that is inclined at the side and bent about the vertical axis. The known heat exchanger having lateral collecting tanks comprises a heat sink through which coolant can flow transversely and which has a longer side at the top and a shorter side at the bottom between the collecting tanks and is formed from a plurality of individual cross tubes. The heat sink as well as the collecting tanks that are fixedly attached to the heat sink with the known heat exchanger are made of metal with the individual components being welded together.
The curved heat sink of the heat exchanger has a smaller bending radius on its upper longer side than the lower shorter side, with the result that the lateral collecting tanks experience torsion, which leads to stresses. These stresses are dissipated via areas of lower strength, often over a very long period of time.
The invention is based on the object of further improving upon a heat exchanger as defined in the introduction and especially facilitating the dissipation of stresses in the case of twisted collecting tanks. Furthermore, an especially economical method of manufacturing such a heat exchanger is to be made available.
This object is achieved with a heat exchanger, whereby according to the basic idea, the collecting tanks are made of a material having much lower strength values than the material of the heat sink.
It is especially preferable if the material of the heat sink has at least 1.5 times, especially approximately 2.5 to 20 times the strength of the material of the collecting tanks. The heat sink is expediently made of metal and the collecting tanks are made of plastic. It is possible for the heat sink to be made of a lightweight metal or a lightweight metal alloy such as an aluminum alloy and for the collecting tanks to be made of a thermoplastic material such as polyamide.
According to a very advantageous exemplary embodiment, the heat sink in the installed position has an oncoming flow surface at the bottom that is chamfered or rounded at the side and has flangeable straps on its lateral connecting planes for attachment to the collecting tanks, these straps being tightly attached to the heat sink with the inclusion of a gasket.
It has proven advantageous for one of the collecting tanks for holding a thermostatic valve that controls the heat exchanger flow as a function of temperature to be integrally connected to a housing. It is likewise regarded as expedient if the collecting tanks are provided with fastening points for mounting on the vehicle and/or attaching other elements.
An especially preferred method for manufacturing such a heat exchanger is characterized in that the collecting tanks are connected to the planar heat sink on its lateral connecting planes and bending of the heat sink is performed subsequently; after this bending, the longer side of the heat sink has a smaller bending radius than the shorter side, so that with the bending of the heat sink, the collecting tanks connected to its lateral connecting planes are twisted.
The stresses that occur in bending the heat sink and the associated twisting of the collecting tanks are advantageously absorbed essentially by the collecting tanks and can be dissipated into the collecting tanks due to the material.
It is highly expedient if the dissipation of stresses into the collecting tanks is supported by means of heat and/or substances that reduce the strength of the material of the collecting tanks.